JPH06295093A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To provide an electrophotographic toner fixable at a low fixing temp., having no problem on anti-offsetting property in practical use and having excellent fixing strength to transfer paper. CONSTITUTION:This electrophotographic toner contains montan ester wax having an absorption peak measured by differential heat analysis within the range of 65-85 deg.C and having <=10mgK0H/g acid value in a component of a bonding resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developer, and more particularly to an electrophotographic toner.

[0002]

2. Description of the Related Art In recent years, copying machines and printers using the electrophotographic method have become widespread, including in general households. Along with the spread, copiers have become more sophisticated, and copiers equipped with a double-sided copy function and equipped with an automatic document feeder are becoming popular.

With the widespread use of copiers, the main purpose is to achieve multi-functionality, lower energy consumption (reduction of power consumption); and to spread to so-called gray areas located at the boundary between the printer and the copier. For the purpose of speeding up; and reducing the machine cost, it is desired to reduce the roll pressure in order to simplify the fixing roll.

In order to meet the above demand, the fixing temperature is low,
A toner having excellent offset resistance and fixing strength is required. In particular, in order to prevent stains during double-sided copying and stains on the automatic document feeder, it is desired to have excellent fixing strength.

The toners for electrophotography which have been widely used conventionally have generally the following compositions. Binder resin 80 to 90% by weight Colorant 5 to 15% by weight Charge control agent 0.5 to 5% by weight Cleaning agent, fluidizing agent, etc. 0.1 to 1% by weight

As can be seen from the above composition, the binder resin occupies most of the toner. Therefore, the physical properties of the binder resin greatly affect the physical properties of the toner. That is, the physical properties of the toner can be controlled by controlling the physical properties of the binder resin.

[0007]

In order to meet the above demands, therefore, a toner has been proposed in which the molecular weight and the molecular distribution of the binder resin are improved as shown below. Specifically, attempts have been made to lower the fixing temperature by reducing the molecular weight of the binder resin. As a result, by lowering the molecular weight of the binder resin, the softening point of the toner is lowered, but at the same time, the viscosity is also lowered, causing another problem that an offset phenomenon to the fixing roll occurs.

In order to solve the problem that the offset phenomenon occurs, an attempt has been made to obtain a binder resin by mixing a resin having a low molecular weight region with a resin having a high molecular weight region. Attempts have also been made to crosslink the polymer portion in the binder resin. However, in these methods, the glass transition point of the resin had to be lowered in order to impart the necessary fixing property to the toner. If the glass transition point of the resin is low, a new problem arises that the storage stability of the toner is impaired.

Further, if a large amount of resin having a low molecular weight region is contained in the binder resin, the toner becomes brittle and the fixing strength becomes a new problem. If the fixing strength of the toner is low,
Specifically, when a document passes through the automatic document feeder, the toner transferred to the paper may be rubbed and adhered by the device, and the toner may further adhere to the document passing through the device, resulting in stains. there were. Especially, there is a possibility that the stain becomes noticeable during double-sided copying.

Further, in order to prevent the occurrence of the offset phenomenon, a method of incorporating a polyolefin-based release agent into the toner has been devised. However, since the polyolefin-based release agent has a high softening point, when it is contained in the toner, the softening point of the toner becomes high. When the softening point of the toner is high, when the toner is fixed at a low fixing temperature, the toner is not sufficiently softened, and a sufficient fixing strength on the transfer paper cannot be obtained.

[0011]

An object of the present invention is to provide an electrophotographic toner which can be fixed at a low fixing temperature, has no practical problem in offset resistance, and has excellent fixing strength on transfer paper. The purpose is to provide.

[0012]

The electrophotographic toner of the present invention has an absorption peak of 65 in the binder resin by differential thermal analysis.
The above object was achieved by containing a montan ester wax having an acid value of 10 to K ° C / 85 ° C and an acid value of 10 mgKOH / g or less.

The electrophotographic toner of the present invention will be described in detail below. The electrophotographic toner of the present invention mainly comprises
It is a particle in which a montan ester wax, a binder resin, a colorant, and other toner components are dispersed. The average particle diameter is 5 to 20 μm.

First, the montan ester wax that is a feature of the electrophotographic toner of the present invention will be described. The montan-based ester wax is a coal-based synthetic wax obtained by bleaching, refining and esterifying crude montan wax extracted from coal (brown coal) using nitric acid, chromic acid or the like.

Since the montan ester wax has a lower softening point than the olefin wax, when it is contained in the electrophotographic toner, the softening point of the toner can be lowered.

The acid value of the montan ester wax used is 10 mgKOH / g or less, which is lower in free fatty acid content in the wax than the general-purpose montan wax. When the content of free fatty acid in the wax is low, it is possible to suppress the unnecessary increase in triboelectric charge amount due to polar groups in the free fatty acid, so it is possible to suppress the increase in triboelectric charge amount that occurs when multiple copies are made. . Therefore, when a montan ester wax having an acid value of 10 mgKOH / g or less is used, good image quality can be obtained. On the other hand, if the acid value of the montan ester wax is larger than 10 mgKOH / g, it is impossible to suppress the increase in the triboelectric charge amount that occurs when a large number of copies are made. Therefore, a practically sufficient image density cannot be obtained.

Further, the absorption peak of the montan ester wax contained in the electrophotographic toner of the present invention by differential thermal analysis is in the range of 65 ° C. to 85 ° C. If the absorption peak is lower than 65 ° C., the storage stability of the toner may be deteriorated, which is not preferable. On the other hand, if the temperature is higher than 85 ° C., the melting start temperature of the toner does not decrease, which is not preferable.

The montan ester wax according to the present invention has an absorption peak by differential thermal analysis of 65 ° C. to 85 ° C.
It has the following and its acid value is 10 mg / KOH / g or less. It is preferable that such a montan ester wax is contained in a range of 1% by weight or more and 20% by weight or less in the resin component composed of the binder resin constituting the toner and the montan ester wax. When the content of the montan ester wax is less than 1% by weight, the effect of including the wax in the toner is not exhibited,
It is not possible to obtain sufficient fixing strength for transfer paper at low temperature. On the other hand, if it is more than 20% by weight, the offset phenomenon easily occurs at a high temperature, which is not preferable.

As the binder resin contained in the electrophotographic toner of the present invention, polystyrene resin, polyacrylic acid ester resin, styrene-acrylic acid ester copolymer resin, styrene-methacrylic acid ester copolymer resin, poly Vinyl chloride, polyvinyl acetate, polyvinylidene chloride,
Examples thereof include phenol resin, epoxy resin, polyester resin and the like.

As the colorant, carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, or a mixture thereof. Etc. can be illustrated.

It is necessary that these colorants are contained in the toner in a ratio suitable for forming a visible image having a sufficient density. Specifically, it is usually added in an amount of 1 part by weight or more and 20 parts by weight or so with respect to 100 parts by weight of the binder resin.

In addition to the binder resin and the colorant, a fluidity improver made of fine silica powder or the like may be added to improve the fluidity of the toner. Furthermore, in order to impart desired physical properties to the toner, a charge control agent, a release agent, a magnetic material and the like can be appropriately dispersed and contained.

The electrophotographic toner of the present invention can be used as a two-component developer by being mixed with a carrier composed of iron powder, ferrite, granulated magnetite or the like. When a magnetic material is contained, it can be used as it is as a one-component developer for developing an electrostatic image without being mixed with a carrier.

[0024]

The electrophotographic toner of the present invention is a montan-based toner having a binder resin component having an absorption peak by differential thermal analysis in the range of 65 ° C. to 85 ° C. and an acid value of 10 mgKOH / g or less. A toner containing an ester wax.

The electrophotographic toner of the present invention contains a wax having an absorption peak by differential thermal analysis in the range of 65 ° C. to 85 ° C. Since it contains a wax having a low softening point, the softening point of the toner itself is lowered.

The electrophotographic toner of the present invention contains a montan ester wax having an acid value of 10 mgKOH / g or less. The montan ester wax having an acid value of 10 mgKOH / g or less has a smaller content of free fatty acids than general-purpose montan wax, and therefore can suppress an unnecessary increase in triboelectric charge amount due to polar groups in the free fatty acids. It is possible to suppress an increase in the triboelectric charge amount that occurs when a large number of copies are made.

[0027]

The present invention will be described in more detail based on the following examples. In the examples, “parts” means “parts by weight”.

Example 1 In this example, toner particles having the composition shown below were prepared. The composition of the toner particles is shown below. -Styrene-acrylic ester copolymer resin 90 parts (Nippon Carbide Industry Co., Ltd., trade name: NC-6550) -Chromium metal dye 1.5 parts (Orient Chemical Industry Co., Ltd., trade name: Bontron S-34) Carbon black 6.5 parts (Mitsubishi Chemical Industries, trade name: MA-100) Montane ester wax 10 parts (Hoechst, trade name: EA-110) However, the differential heat of the above montan ester wax. The analytical absorption peak is at 71 ° C and the acid value is 5.0 mg KO.
It was H / g.

The raw materials having the above composition are mixed with a super mixer, melt-kneaded with a twin-screw kneader, pulverized with a jet mill, and then classified with a dry air stream classifier to have an average particle diameter of 10 μm. To obtain toner particles. Then, with respect to 100 parts of the obtained toner particles, hydrophobic silica (manufactured by Cabot Corporation, trade name: Cabosil TS-53
0.4 part of 0) was added and the mixture was stirred in a Henschel mixer for 1 hour to adhere the above-mentioned hydrophobic silica to the surface of the obtained toner particles to obtain an electrophotographic toner of this example.

Example 2 In this example, toner particles having the following composition were prepared. The composition of the toner particles is shown below. -Styrene-acrylic ester copolymer resin 90 parts (Nippon Carbide Industry Co., Ltd., trade name: NC-6550) -Chromium metal dye 1.5 parts (Orient Chemical Industry Co., Ltd., trade name: Bontron S-34) Carbon black 6.5 parts (Mitsubishi Chemical Industries, trade name: MA-100) Montane ester wax 10 parts (Hoechst, trade name: EA-110) However, the differential heat of the above montan ester wax. The absorption peak by analysis is at 71 ° C and the acid value is 7.2 mg KO.
It was H / g.

The process for obtaining a toner using the raw material having the above composition was carried out in the same manner as in Example 1.

Example 3 In this example, toner particles having the following composition were prepared. The composition of the toner particles is shown below. -Styrene-acrylic ester copolymer resin 90 parts (Nippon Carbide Industry Co., Ltd., trade name: NC-6550) -Chromium metal dye 1.5 parts (Orient Chemical Industry Co., Ltd., trade name: Bontron S-34) Carbon black 6.5 parts (Mitsubishi Chemical Industries, trade name: MA-100) Montane ester wax 10 parts (Hoechst, trade name: F) However, the differential thermal analysis of the above montan ester wax F Absorption peak at 80 ℃, acid value 6.5mgK
It was OH / g.

The process of obtaining a toner using the raw material having the above composition was performed in the same manner as in Example 1.

Example 4 In this example, toner particles having the following composition were prepared. The composition of the toner particles is shown below. -Styrene-acrylic acid ester copolymer resin A 90 parts (Nippon Carbide Industry Co., Ltd., trade name: NC-6550) -Chromium metal dye 1.5 parts (Orient Chemical Industry Co., Ltd., trade name: Bontron S-34) ) Carbon black 6.5 parts (Mitsubishi Chemical Co., Ltd., trade name: MA-100) Montane ester wax 10 parts (Hoechst, trade name: F) However, the differential heat of the above montan ester wax F The absorption peak by analysis is at 80 ° C and the acid value is 8.1mgK.
It was OH / g.

The process for obtaining the toner using the raw material having the above composition was carried out in the same manner as in Example 1.

Comparative Example 1 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that the montan ester wax was not mixed.

Comparative Example 2 Comparative Example 2 was repeated in the same manner as in Example 1 except that 10 parts of polypropylene wax (manufactured by Sanyo Chemical Industry Co., Ltd., trade name: VISCOL 550P) was mixed in place of the montan ester wax. To obtain a toner for electrophotography.

(Comparative Example 3) Acid value 6.5 mg KOH / g
Instead of the montan ester wax (trade name: F) having an absorption peak by differential thermal analysis at 80 ° C., a montan having an acid value of 22 mgKOH / g and a differential thermal analysis peak at 87 ° C. A comparative electrophotographic toner was obtained in the same manner as in Example 3 except that 10 parts of the ester ester wax (trade name: KP) was mixed.

(Comparative Example 4) Acid value 6.5 mg KOH / g
In place of the montan ester wax (trade name: F) having an absorption peak by differential thermal analysis at 80 ° C., the acid value is 33 mgKOH / g, and the peak by differential thermal analysis at 89 ° C. is montan. A comparative electrophotographic toner was obtained in the same manner as in Example 3 except that 10 parts of a system ester wax (trade name: KSS) was mixed.

(Comparative Example 5) Acid value 6.5 mg KOH / g
In place of the montan ester wax (trade name: F) whose absorption peak by differential thermal analysis exists at 80 ° C., the acid value is 12 mgKOH / g, and the montan whose differential thermal analysis peak exists at 80 ° C. A comparative electrophotographic toner was obtained in the same manner as in Example 3 except that 10 parts of the ester ester wax (trade name: F) was mixed.

Next, Examples 1 to 4 and Comparative Example 1
The following items were tested using the electrophotographic toners obtained in No. 5 to No. 5.

(1) Non-offset temperature range test First, 4 parts of the electrophotographic toners obtained in the above-mentioned Examples and Comparative Examples were coated with a ferrite carrier (made by Powder Tech Co., trade name). : FL-10
96 parts of 20) were added and mixed to prepare a two-component developer. Next, the obtained two-component type developer was filled in a commercially available copying machine (manufactured by Sharp Corporation, trade name: SF-9800), and a belt-shaped unfixed image of 2 cm in length and 5 cm in width was formed on an A4 transfer paper. Created multiple. After that, a fixing machine in which a heat fixing roll having a surface layer made of Teflon and a pressure fixing roll having a surface layer made of silicone rubber are paired and rotated, a roll pressure is 1 Kg / cm ² , and a roll speed is 100 m.
The surface temperature of the heat fixing roll was changed stepwise, and the toner image was fixed on the transfer paper having the unfixed image at each surface temperature. It was visually observed whether or not the toner was smeared in the margin portion, and the temperature region in which the toner was not smeared was defined as the non-offset temperature region.

(2) Fixing Strength Test The surface temperature of the heat fixing roll of the fixing device was set to 150 ° C. and 170 ° C., and the toner image of the transfer paper on which the unfixed image was formed was fixed. The resulting fixed image was rubbed with a cotton pad. The image density of the fixed image before rubbing and the image density of the fixed image after rubbing were measured using a reflection densitometer (trade name: RD-914, manufactured by Macbeth Co.).
Then, the obtained measured value was applied to the following formula to calculate the fixing strength.

Fixing strength (%) = (image density of fixed image after rubbing / image density of fixed image before rubbing) × 100

(3) Multi-sheet copy test Each developer obtained in the pre-test (1) was filled in a commercially available copying machine (manufactured by Sharp Corporation, trade name SF-9800) and
0000 continuous copies were made. Initial and 1000
The triboelectric charge amount and the image density were measured after continuous copying of 0 sheets. The size of the original used for copying is A4, and 10% of it is a black part. The triboelectric charge amount is
Blow-off frictional static electricity measuring device (manufactured by Toshiba Chemical Co., trade name: TB-200), and image density was measured using a reflection densitometer (manufactured by Macbeth Co., trade name: RD-914). The test results are shown in Table 1 and Table 2.
Shown in.

[0046]

[0047]

As is clear from the test results shown in Table 1, the non-offset temperature range of the electrophotographic toners obtained in Examples 1 to 4 ranges from low temperature to high temperature,
The temperature range was 65 ° C to 70 ° C. Therefore,
It was confirmed that the electrophotographic toners obtained in Examples 1 to 4 had a practically sufficient non-offset temperature region.

When the fixing temperature is 150 ° C., the toners obtained in Examples 1 to 4 have a fixing strength of 60% or more. Therefore, it was found that the toners obtained in Examples 1 to 4 had a sufficiently high fixing strength even at a low temperature and were fixed on the original.

Further, when the toners obtained in Examples 1 to 4 were continuously copied on 10,000 sheets, there was almost no difference between the initial triboelectric charge amount and the triboelectric charge amount after continuous copying.
It was stable. In addition, the image density also showed almost no difference between the initial value and the value after continuous copying. Therefore, it was confirmed that the toners obtained in Examples 1 to 4 can maintain the high density as much as the initial value even after being used for continuous copying of 10,000 sheets.

On the other hand, in particular, it was confirmed that the developers using the toners obtained in Comparative Examples 1 and 2 can obtain a fixing strength as low as 45% at a fixing temperature of 150 ° C. Further, in the developers using the toners obtained in Comparative Examples 3 to 5, the triboelectric charge amount increased after copying a large number of sheets. In addition, there was a considerable difference in the image density between the initial value and the value after continuous copying. Therefore, it was confirmed that the developers using the toners obtained in Comparative Examples 3 to 5 cannot withstand the multiple copy.

[0052]

The toner for electrophotography according to the present invention has an absorption peak in the binder resin by differential thermal analysis of 65 ° C to 85 ° C.
A toner comprising a montan ester wax having an acid value of 10 mgKOH / g or less at a temperature of 0 ° C. Since the montan ester wax has a low softening point, the softening point of the toner itself is lowered. Therefore, the electrophotographic toner of the present invention can be fixed at a low fixing temperature.

The electrophotographic toner of the present invention contains a montan ester wax having an acid value of 10 mgKOH / g or less. The montan ester wax having an acid value of 10 mgKOH / g or less has a smaller content of free fatty acids than general-purpose montan wax, and thus an unnecessary increase in triboelectric charge due to polar groups in the free fatty acids is suppressed. Therefore, it is possible to suppress an increase in the triboelectric charge amount that occurs when a large number of copies are made. Further, since the electrophotographic toner of the present invention has releasability by using a specific montan wax, it does not have any practical problem in offset resistance, and the transfer paper The fixing strength to is also excellent.

Claims (2)

[Claims] 1. A binder resin component comprising a montan ester wax having an absorption peak by differential thermal analysis in the range of 65 ° C. to 85 ° C. and having an acid value of 10 mgKOH / g or less. Characteristic electrophotographic toner. 2. The toner for electrophotography according to claim 1, wherein the montan ester wax is contained in a range of 1% by weight or more and 20% by weight or less.